2.  A state of temporary & reversible loss of awareness and reflex reactions induced by drugs to render surgery painless, possible & comfortable.  General anesthesia for surgical procedure to render the patient unaware / unresponsive to the painful stimuli.

3.  GABA: major inhibitory neurotransmitter (point of action of anesthetic drugs)  Membrane structure and function: future of the anesthesiology  Glutamate: major excitatory neurotransmitter  Endorphins: analgesia.  Unitary hypothesis of the inhalation agents.

4.  Act in different ways at the level of the central nervous system.  Disrupt normal synaptic transmission - interfering with release of neurotransmitters from pre-synaptic nerve terminal (enhance or depress excitatory or inhibitory transmission). - altering re-uptake of neurotransmitters, - Changing the binding of neurotransmitters to the post-synaptic receptor sites or - Influencing the ionic conductance change that follows activation of the post-synaptic receptor by neurotransmitters.

5.  Meyer-Overton Theory postulates that it is the number of molecules dissolved in the lipid cell membrane.  Protein Receptor Hypothesis postulates that protein receptors in the central nervous system.  Activation of GABA receptors.  may inhibit certain calcium channels and therefore prevent the release of neurotransmitters and inhibit glutamate channels.

6.  Nitrous oxide  Halothane (Fluothane)  Methoxyflurane (Penthrane)  Enflurane (Ethrane)  Isoflurane (Forane)  Desflurane (Suprane)  Sevoflurane (Ultane)

8. STRUCTURE OF DIETHYL ETHER

9. N=N=O Nitrous Oxide Halothane Enflurane F H F – C – C* – Br F Cl F F F Cl – C* – C – O – C – H H F F F H F F– C – C* – O – C – H F Cl F Isoflurane F F H H C F C O C F F C H F F Sevoflurane F H F F – C – C* – O – C – H F F F Desflurane

10. - Aliflurane - Chloroform - Cyclopropane - Diethyl ether - Enflurane - Ethylene - Halothane - Methoxyflurane - Methoxypropane - Roflurane - Teflurane - Trichloroethylene - Vinyl ether

11.  It is a chemical compound possessing general anesthetic properties that can be delivered via inhalation.  They are administered by anesthetists (anesthesiologists, nurse anesthetists, and anesthesiologist assistants) through an anesthesia mask, LMA or ETT connected to some type of anesthetic vaporizer and an anesthetic delivery system.

12.  Inhalational anesthesia refers to the delivery of gases or vapors from the respiratory system to produce anesthesia  Pharmacokinetics-- uptake, distribution, and elimination from the body.  Pharmacodyamics - MAC value.

13.  Inhaled anesthetic agents remain popular for maintenance and induction of anesthesia.  Inhalation induction is the technique of choice for:  Predicted difficult airway.  Difficult intravenous access.  Needle phobia, including children.

14.  1845 - Horace Wells- N 2 O  1846 - William Morton- Ether  1847 - Simpson- Chloroform  1934 - Cyclopropane  1956 - Halothane

15.  Pharmacokinetics: how the body affects the drug  Pharmacodymanics: how the drugs affects the body

16.  Solubility in blood  Alveolar blood flow  Differences in partial pressure between alveolar gas and venous blood  Therefore: low output states predispose patients to overdosage of the soluble agents

17.  Biotransformation: cytochrome P- 450 (specifically CYP 2EI)  Transcutaneous loss or exhalation  Alveolus is the most important in elimination of the inhalation agents  Diffusion hypoxia” and the nitrous oxide

18.  Redistribution from brain to blood to air  Anesthetics that are relatively insoluble in blood and brain are eliminated faster

19.  The concentration of a gas in a mixture of gases is proportional to the partial pressure.  Inverse relationship between blood : gas solubility and rate of induction.

20.  Increase in inspired anesthetic concentration will increase rate of induction  Direct relationship between ventilation rate and induction rate  Inverse relationship between blood flow to lungs and rate of onset  MAC = minimum concentration in alveoli needed to eliminate pain response in 50% of patients

21.  Amnesia / Unconsciousness  Analgesia  Muscle relaxation

22.  Anesthesia defined as the abolition of sensation  Analgesia defined as the abolition of pain “Triad of General Anesthesia”  Need for Unconsciousness  Need for Analgesia  Need for Muscle relaxation

23.  Stage I : Analgesia  Stage II : Excitement, combative behavior – dangerous state  Stage III : Surgical anesthesia  Stage IV : Medullary paralysis – respiratory and vasomotor control ceases.

24.  Anesthetics are associated with - Decrease in systemic blood pressure – myocardial depression and direct vasodilatation. - Blunting of baroreceptor control and decreased central sympathetic tone.

25.  Reduce metabolic rate of the brain  Decrease cerebral vascular resistance thus increasing cerebral blood flow = increase in intracranial pressure

26. The main target of inhalation anesthetics is the brain.

27.  The important characteristics of Inhalational anesthetics which govern the anesthesia are :  Solubility in the blood (blood : gas partition co-efficient)  Solubility in the fat (oil : gas partition co- efficient)

29. BLOOD GAS PARTITION COEFFICIENT Agents with low solubility in blood quickly saturate the blood. The additional anesthetic molecules are then readily transferred to the brain.

30. Blood gas partition co-efficient affecting rate of induction and recovery

31. OIL GAS PARTITION CO-EFFICIENT Higher the Oil: Gas Partition Co-efficient lower the MAC. E.g., Halothane 1.4 220 0.8

32.  Oil: gas partition co-efficient:  It is a measure of lipid solubility.  Lipid solubility - correlates strongly with the potency of the anesthetic.  Higher the lipid solubility – potent anesthetic. e.g., halothane

33.  Pleasant odor  Non-irritant  Low blood gas solubility.  Chemically stable.  Non inflammable.  Potent.  Inert.  Not metabolized.  Non-toxic.  Analgesic.  No Cardiovascular & respiratory depression.

35.  Concentration of inhaled anaesthetics in the alveolar gas that prevents movements in 50% of patients in response to a standardized stimulus (eg surgical incision)  MAC is important to compare the potencies of various inhalational anesthetic agents.  1.2-1.3 MAC prevent movement in 95% of patients.

36.  MAC value is a measure of inhalational anesthetic potency.  It is defined as the minimum alveolar anesthetic concentration ( % of the inspired air) at which 50% of patients do not respond to a surgical stimulus.  MAC values are additive and lower in the presence of opioids.

37.  MAC awake: MAC allowing voluntary response to command in 50% of patients  MAC 95%: MAC that prevents movement in 95 % of patients  MAC intubation: MAC that allows intubation without muscle relaxant, coughing or bucking in 50% of patients.  MAC-BAR (1.7-2.0 MAC), which is the concentration required to block autonomic reflexes to nociceptive stimuli.

38.  Hyperthermia.  Chronic drug abuse (Ethanol).  Acute use of amphetamines.  Hyperthyroidism.  Reducing age.

39.  Increasing Age.  Hypothermia.  Other anesthetic (Opioids).  Acute drug intoxication (Ethanol).  Pregnancy.  Hypothyroidism.  Other drugs ( Clonidine,Reserpine).

40.  Gender  Duration of anesthesia  Carbon dioxide tension (21-95 mmHg)  Metabolic Acid base status  Hypertension  Hyperkalemia

41. Inhalation Anesthetic MAC value % Oil: Gas partition Nitrous oxide104 1.4 Desflurane7.323 Sevoflurane2.0553 Isoflurane1.1591 Halothane0.77220

42.  N2O = 105%  Halothane = 0.75%  Isoflurane = 1.15%  Euflurane = 1.68%  Sevoflurane = 2%  Deslurane = 6%  N 2 O alone is unable to produce adequate anesthesia ( require high conc. )

43. 1.Increasing the delivered concentrations of anesthetic 2.The gas flow rate through the anesthetic machine 3.Increasing minute ventilation MV = Respiratory Rate × Tidal volume

44. 1)The rate of blood flow to the brain 2)The solubility of the inhalational agent in the brain 3)The difference in the arterial and venous concentration of the inhalational agent

45.  Increase FGF rate.  Decrease Breathing System Volume.  Decrease absorption of the breathing system of the anesthetic machine.  All closer inspired gas concentration to the fresh gas concentration.

46.  The greater uptake of an anesthetic agent; the lower rate of rise of FA  The greater difference between Fi and Fa; the slower the rate of induction  The higher the blood gas solubility coefficient; the greater the anesthetic solubility, and the slower the onset of induction and recovery.  Increased alveolar blood flow increases anesthetic uptake.

47.  Solubility in blood  Alveolar blood flow  Partial pressure difference between alveolar gas & venous blood (PA- PV)

48.  Mainly ventilation perfusion mismatching  Normally, alveolar and arterial anesthetic pressures are assumed to be equal.  Presence of ventilation perfusion mismatching increases alveolar arterial differences

49.  Ventilation  Concentration  Apparatus Dead Space

50. Types of Tissues CO%Relative Solubility Vessel rich group: Brain, heart, liver, kidney, endocrine glands 751 Muscle group: Skin & Muscles 191 Fat group:620 Vessel poor group: Bone, ligaments, teeth, hair & cartilages 00

51. Nitrous oxide  Safest inhalational anesthetic.  Weak anesthetic but a good analgesic.  No toxic effect on the heart, liver and kidney.  Caution about diffusional hypoxia.  Megaloblastic anemia.

52. Physical Property:  laughing  Not flammable  Odorless  Colorless  Tasteless

53.  Prepared by Priestly in 1776  Anesthetic properties described by Davy in 1799  Characterized by inert nature with minimal metabolism  Colorless, odorless, tasteless, and does not burn

54.  Simple linear compound  Not metabolized  Only anesthetic agent that is inorganic

55.  Minimal effects on heart rate and blood pressure  May cause myocardial depression in sick patients  Little effect on respiration  Safe, effective agent

56.  Manufacturing impurities toxic  Hypoxic mixtures can be used  Large volumes of gases can be used  Beginning of case: second gas effect  End of case: diffusion hypoxia

57.  Major difference is low potency  MAC value is 105%  Weak anesthetic, powerful analgesic  Needs other agents for surgical anesthesia  Low blood solubility (quick recovery)

58.  Inhibits methionine synthetase (precursor to DNA synthesis)  Inhibits vitamin B-12 metabolism  Dentists, OR personnel, abusers at risk

59.  Good Analgesic  Weak anesthetic  Excreted via lungs  MAC = 105%  Lower water solubility  Not Metabolized in the body

60.  Diffusion Hypoxia.  Closed gas spaces (N 2 O can diffuse 20 times faster into closed spaces than it can be removed, resulting in expansion of pneumothorax, bowel gas, or air embolism or in an increase in pressure within noncompliant cavities such as the cranium or middle ear.  CVS depression  Toxicity  Teratogenic

61.  A decrease in PO 2 usually observed as the patient is emerging from an inhalational anesthetic where N 2 O was a component.  The rapid outpouring of insoluble N 2 O can displace alveolar oxygen, resulting in hypoxia.  All patients should receive supplemental O 2 at the end of an anesthetic and during the immediate recovery period.

62. Concentration effect states that with higher inspired concentrations of an anesthetic, the rate of rise in arterial tension is greater.

63. The ability of the large volume uptake of one gas (first gas) to accelerate the rate of rise of the alveolar partial pressure of a concurrently administered companion gas (second gas).

64. Usually refers to nitrous oxide combined with an inhalational agent. Because nitrous oxide is not soluble in blood, its' rapid absorption from alveoli causes an abrupt rise in the alveolar concentration of the other inhalational anesthetic agent.

65.  It is a potent anesthetic.  Induction is pleasant.  It sensitizes the heart to catecholamines.  It dilates bronchus – preferred in asthmatics.  It inhibits uterine contractions.  Halothane hepatitis and malignant hyperthermia can occur.

66.  Sweet and ethereal odor.  Generally do not sensitizes the heart to catecholamines.  Seizures occurs at deeper levels – contraindicated in epileptics.  Caution in renal failure due to fluoride.